The Collaborative International Dictionary of English v.0.48:

Ann \Ann\, Annat \An"nat\, n. [LL. annata income of a year,
   also, of half a year, fr. L. annus year: cf. F. annate
   annats.] (Scots Law)
   A half years's stipend, over and above what is owing for the
   incumbency, due to a minister's heirs after his decease.
   [1913 Webster]